The US government is taking aim at what has been an indomitable empire: Google’s ubiquitous search engine that has become the internet’s main gateway.

The legal attack will swing into full force Tuesday in a Washington DC federal courtroom that will serve as the battleground for the biggest US antitrust trial since regulators went after Microsoft and its dominance of personal computer software a quarter century ago.

The 10-week trial before US District Judge Amit Mehta is expected to include potentially revelatory testimony from top executives at Google and its corporate parent Alphabet, as well as other powerful technology companies. Alphabet CEO Sundar Pichai, who succeeded Google co-founder Larry Page in 2019, will be among the most prominent witnesses likely to testify. Court documents also indicate one of Apple’s highest-ranking executives, Eddy Cue, might be called to the stand.

The case against Google mirrors the one brought against Microsoft in many ways, including the existential threat it poses to a renowned tech giant whose products are relied on by billions of people.

The trial is scheduled to continue into late November before its first phase wraps, after which another round of court filings and arguments are expected. Mehta isn’t expected to issue a ruling until early next year. If he decides Google has been breaking the law, it will trigger another trial to determine what measures should be taken to rein in the Mountain View, California, company.

Although Google products such as the Chrome web browser, Gmail, YouTube and online maps all are hugely popular, none have become as indispensable — or as valuable — as the internet search engine invented by Page and a fellow Stanford University graduate student, Sergey Brin, during the late 1990s.

The trial is beginning just a couple weeks after the 25th anniversary of the first investment in the company — a $100,000 check written by Sun Microsystems co-founder Andy Bechtolsheim that enabled Page and Brin to set up shop in a Silicon Valley garage.

Today, Google’s corporate parent, Alphabet Inc, is worth $1.7 trillion and employs 182,000 people, with most of the money coming from $224 billion in annual ad sales flowing through a network of digital services anchored by a search engine that fields billions of queries a day.

Google could be hobbled if the antitrust trial culminates in concessions that undercut its power. One possibility is that the company could be forced to stop paying Apple and other companies to make Google the default search engine on smartphones and computers.

Nearly three years after filing its antitrust lawsuit during the Trump administration, lawyers from the US Justice Department will try to prove Google has been abusing the power of its search engine to stifle competition in ways that discouraged innovation. Critics say the quality of search results has deteriorated, too, as Google used its engine to sell ads and promote its own products, like Google restaurant reviews instead of those offered by Yelp.

Dozens of state attorneys general, led by Colorado, have waded into the battle and will have a chance to prove Google turned into an illegal monopoly that’s harming consumers.